Dissolver systems, liquid color concentrate

The earliest commercial methods used slurry polymerizations with liquid hydrocarbon diluents, like hexane or heptane. These diluents carried the propylene and the catalyst. Small amounts of hydrogen were fed into the reaction mixtures to control molecular weights. The catalyst system consisted of a deep purple or violet-colored TiCls reacted with diethyl aluminum chloride. The TiCb was often prepared by reduction of TiCU with an aluminum powder. These reactions were carried out in stirred autoclaves at temperatures below 90 °C and at pressures sufficient to maintain a liquid phase. The concentration of propylene in the reaction mixtures ranged between 10-20%. The products formed in discrete particles and were removed at 20-40% concentrations of solids. Unreacted monomer was withdrawn from the product mixtures and reused. The catalysts were deactivated and dissolved out of the products with alcohol containing some HCl, or removed by steam extraction. This was followed by extraction of the amorphous fractions with hot liquid hydrocarbons. 

---